Certain ether peroxides derivable from alpha-substituted vinyl ethers

ABSTRACT

THE INVENTION CONCERNS ETHER PEROXIDES HAVING AN ETHER OXYGEN AND A PEROXY GROUP OXYGEN ATTACHED TO A COMMON CARBON ATOM, THAT IS: R3-O-C(-R2)(-R4)-O-O-R1 WHERE THE R&#39;&#39;S ARE SPECIFIED HYDROCARBON RADICALS. EXAMPLES ARE: 2-METHOXY -2-CUMYLPEROXY PROPANE, 1-METHOXY-1-T-BUTYLPEROXY-3,35-TRIMETHYLCYCLOHEANE, 2METHYL-2-T-BUTYLPEROXY-TETRAHYDROPYRAN, AND 1,3,5TRIS(ALPHA(2-ISPROPOXY-2:PROPYLPEROXY)ISOPROPYL) BENZENE.

United States Patent 01 ice ABSTRACT OF THE DISCLOSURE The inventionconcerns ether peroxides having an ether oxygen and a peroxy groupoxygen attached to a common carbon atom, that is:

where the Rs are specified hydrocarbon radicals. Examples are: Z-methoxy2 cumylperoxy propane; l-methoxy l-t-butylperoxy3,3,S-trimethylcyclohexane; 2- methyl 2 t butylperoxy-tetrahydropyran;and 1,3,5- tris[alpha(2 ispropoxy 2 propylperoxy)isopropyl] benzene.

This invention relates to novel ether peroxides having an ether oxygenand a peroxy group oxygen attached to a common carbon atom.

The novel ether peroxides of the invention have the formula:

where R R R R and Z are radicals having the following identities:

(a) R is aliphatic, cycloaliphatic, or

(b) R R and R are aliphatic, cycloaliphatic or aromatic;

(c) R is aliphatic or cycloaliphatic;

(d) Z is H; and 1 (e) C, R and OR together, or C, R and R Z together,may form a ring.

Herein peroxy" or dioxy refers to the -OO- group and hydroperoxy refersto the OOH group.

In all instances the numerical subscript following R is being used as anidentification tag only and is not intended to indicate the presence ofmore than one of said KS.

3,822,317 Patented July 2, 1974 A need exists for radical initiatorsoperable in the peroxyester temperature range but which do not containcarbonyl groups. Carbonyl residues on polymer chains have beenconsidered to be the cause of poor light and oxidative stability inseveral commercial polymers.

Several resin manufacturers have expressed an interest in thepossibility of using a dialkyl peroxide that would have a half-life nearthat of t-butyl perbenzoate. Three unsymmetrical dialkyl peroxides wereprepared; they were too thermally stable to be replacements forperoxyesters.

The diperoxyketals have half-lives in the peroxyester range but arereported to be very shock sensitive. The preparation of peroxyketals waspatented by Shell in 1946 but the compounds were never offered on acommercial scale presumably because of their hazardous nature.

The principal object of this invention is to provide peroxides whichhave substantially the effectiveness of commercial peroxyesters, e.g.,t-butyl perbenzoate.

Broadly, this object has been attained by the discovery of the etherperoxides I as defined above. It is preferred that R be an aliphatichydrocarbon radical joined to the -OO group through a tertiary carbonatom, for example, t-butyl, t-pentyl and cumyl. It is preferred that R,and R be lower alkyl having 1-8 carbon atoms, for example, methyl andisopropyl.

The ether peroxides I of the invention have been defined very broadly interms of R and Z; however it is to be understood R and Z are notcritical to the ability of the compounds to be made or to the utility ofthe compounds as radical initiators for polyester curing or otherreactions promoted by peroxyester and peroxides.

a-sub vinyl ethers Some ethers of this type needed for use in the Roppprocess for preparing compounds of the invention are availablecommercially. Many methods for preparing these ethers are known, forexample.

1. Armitage, D. and Wilson, C., J. Am. Chem. Soc., 81 2437 (1959).

2. Ansell, M. and Thomas D., J. Chem. Soc., 1163 (1958).

3. Trubnikov, I. and Pentin Yu., Zh. Obsch. Khim., 32, 3590 (1962).

4. Winstein, S. and Ingraham, L., J. Am. Chem. Soc., 77, 1741 (1955).

5. Dolliver, M., Gresham, T., Kistiakowsky, G., Smith, E., and Vaugh,W., J. Am. Chem. Soc., 60, 440 (1938).

6 The commercial base-catalyzed addition of alcohols to acetylenes.

7. The catalytic cracking of ketals over acid catalysts such as hydrogenchloride, sultonic acid, and p-toluene sulfonic acid.

Preparation of a-sub cyclic vinyl ether 1-Methoxy-3,3,5-trimethylcyclohexene Here the ketal was not isolated but converteddirectly to the unsaturated ether.

A two-liter round bottom flask was equipped with a two-foothelices-packed column and a variable reflux take-off head. Attached tothe take-01f head thermometer was the Thermocap relay used to activate aFlexopulse timer set at a 10 to l reflux ratio.

In a 500 ml. flask was placed 70 g. (0.5 mole) of 3,3,5-trimethylcyclohexanone, 52 g. (0.5 mole) of 2,2-dimethoxypropane, 32 g.(1.0 mole) of methanol, 100 g. of cyclohexane and 0.1 g. ofp-toluenesulfonic acid. The Thermocap relay was set at 52, the boilingpoint of the acetone-methanol-cyclohexane ternary azeotrope.

When the vapor temperature could not be kept at 52, the Thermocap wasdisconnected and distillation continued at 10 to 1 reflux ratio. Thebath temperature was raised slowly to 190 (temperature of vapor neverrose above 56). When no further distillate came over, the oil bath wasremoved, the pot residue allowed to cool and sodium methoxide was addedto neutralize the catalyst.

The pot residue was then distilled under reduced pressure through a 15inch Vigreux column giving 71.5 g. of1-methoxy-3,3,S-trimethylcyclohexene, boiling at 62- 64 at 13 mm.pressure, n '=l.4508 The weight yield was 90.4% but analysis by vaporphase chromatography showed the presence of 9.6% ketone in the ether.The true yield was 82.5%.

All temperatures are degrees, Centigrade. The material was used as is insubsequent reactions with no deleterious effects.

Preparation of Compounds of the Invention Compounds of this inventioncan be made by at least two published procedures: Kharasch and Fone, J.Org. Chem. 23 324 (1958) and Ropp, S. Patent No. 2,776,319 (Jan. 1,1957). It is preferred to use a new method which is disclosed in U.S.patent application Ser. No. 585,295 filed Oct. 10, 1966 by RichardAnthony Bafford, Leonard Ernest Korczykowski and Orville Leonard Mageli.

Illustration A This preparation by the method of Korasch-Fono wascarried out under nitrogen in a four-necked round bottomed flaskequipped with stirring, dropping funnel, reflux condenser andthermometer.

A 10% solution of cobalt octoate (6%) in benzene was used as catalyst.

Reaction of isopropyl ether with t-butyl hydroperoxide To a well stirredmixture of 208 g. isopropyl ether (2 mole), 800 ml. of benzene and 390drops of cobalt catalyst heated at 70il C. was added dropwise over aperiod of three hours, 400 g. of t-butyl hydroperoxide 90%. The mixturewas allowed to reflux for 24 hours. At the end of this time the mixturewas filtered off and the solvent evaporated under reduced pressure. Theresidue was diluted with pentane and washed with 10% NaOH solution.

The pentane layer was washed to neutral dried over anhydrous MgSOfiltered and the solvent evaporated under reduced pressure. A yield of24 g. was obtained.

Purification by vapor phase chromatography (VPC) gave two products:

CHI CH5 CH3 CH3 (1) CH| -O-COOC(CHa)a (2) CHa--Q--OOCKCHQ: O a... a.Ha):

For (1): Theoretical (percent): C, 60.37; H, 10.87. Found (percent): C,60.22; H, 10.99.

4 For (2): Theoretical (percent): C, 63.25; H, 11.58. Found (percent):C, 63.45; H, 11.91.

These compounds of this invention have been named: (See (1) and (2) onpage 7.)

Illustration B The method of Ropp was used. Methyl isopropenyl ether wasadded to a cold (0-5") ethereal solution of tbutyl hydroperoxide and acatalytic quantity (one drop) of concentrated sulfuric acid. Thereaction is exothermic and the temperature was controlled by the rate ofaddition of the vinyl ether and external cooling. The mixture was thenstirred several hours although it is very likely that the reaction isvery fast. The reaction mixture was washed with 10% potassium hydroxideto destroy the catalyst and to remove any excess hydroperoxide. Theethereal solution was then washed with water, dried over sodium sulfateand stripped in vacuo.

(l) Bis (2,2-t-butylperoxy) diisopropyl ether.

(2) 2-isopropoxy-2-t-butylperoxy propane.

The active oxygen assays were consistently greater than theoretical eventhough unreacted hydroperoxide was completely absent from the products.It was at first believed that the fa ult lay with the assay method. Asample of 2-methoxy-2-t-butylperoxy propane wasdistilled under reducedpressure through a short column. Although the material distilled over anarrow range, a VPC scan at on a 6 foot diisodecyl phthalate on 60- 80WAW810 column showed two sharp bands one at 13.7 min., the other at 40.4min. By careful fractionation, two fractions were separated. Fraction Bdistilled at 36- 41 at 4-5 mm.; n 1.3995; active oxygen 10.07% (theoryfor 2-methoxy-2-t-butylperoxy propane 9.87%).

Fraction A distilled at 44-46" at 4-5 mm; n 1.4063; active oxygen 14.2%(theory for 2,2-bis-t-butylperoxy propane 14.5%). That fraction A was2,2-bis-t-butylperoxy propane was established by the synthesis of anauthentic sample from acetone and t-butyl hydroperoxide (its properties;active oxygen 14.3%; 1.4064). The infrared spectrum of fraction A andauthentic 2,2-bis(tbutylperoxy) propane were superimposable.

The compounds of the invention which are of special interest because oftheir structure are illustrated:

Named: 1,3,5-tris-[a(2-isopropoxy-Z-propylperoxy)isopropyl]benzene.

Many ether peroxides of the invention were prepared. In somepreparations, the product was not separated to obtain the essentiallypure ether peroxide, as shown by an active oxygen [A.O.] assay overThese ether peroxides are listed in Table 1.

TABLE 1 [14.0 Yield, assay] Ether peroxide m)" percent percent 1-2-methoxy-2-t-butylperoxy propane 1. 4022 75 113 do -1. 3971 72 98.1 2.2-etloxy-2-t-butylperoxy propane a 1. 4020 85 125 0.---.- 5 2-lsopropoxt-butylperoxy propane 1. 3980 91 97. 4 6- 2-isobutoxy- -butylperoxypropane... 1. 4023 99. 5 95 7- 2-Inethoxy-2-eumylperoxy propane- 1. 500185 105 8- a-Methoxy-a-t-butylperoxyethyl benzene 1. 4841 86 95. 61-methoxy-i-t-butylperoxyeyelopentane d 1. 4302 e 18 99. 41-methoxy-1-t-butylperoxycyelohexane.- 1. 4396 84 98. 3l-methoxy1-t-butylperoxycyeloheptane 1. 4496 68 98. 61-methoxy-1-t-butylperoxy-3,3,5-trimethylcyelo- 1. 4419 66 104. 6hexane. 85 96. 5 13- 2-methyl-2-t-butylperoxytetrahydroiuran R 77 96. 314 2-meth I-Z-t-butylperoxytetrahydropyran- 91 100 15. 3,4-bis Ka-dimethyl-a-(2-ethoxy-2'-propyl 80 methyl] isopro ylbenzene. 16.2,53-dimethyl-2,5- 2'-ethoxypropyl-2-peroxy) hexyne- 1. 4821 74 17-1-ethoxy-1-t-butylperoxyeyclopenteue h 1. 4315 85 102 B.P. 36-41 at 4-5mm.

* Yield 1s quantitative, some product is lost in stripping. 'B.P. 37-39"at 3 mm.

' B.P. 28-29 at 0.5 mm

B The crude yield was 87269., (0.15 mole run) but assayed 116% oftheory. This was separated by fractional distillation into 9.54 g. of1,l-bis-t-butylperoxycyelopentane; active oxygen 12.23% (theory 13.00%)and 5 g. of l-methoxy-l-t-butylperoxyeyclopentane; active oxygen 8.51%(theory 8.54%).

Prepared from 2-methyl-4,5-dihydrofuran. I Prepared from 2-methylenotetrahydroiuran. 13.1. 3840 at 0.06 mm.

Thermal Stability of Ether Peroxides The half-lives and specific rateconstants for the decomposition of dilute benzene solutions of etherperoxides are listed in Tables 2 and 3. Determinations were at 100unless otherwise specified. The half-lives of some well-known peroxidesare included for comparison.

In Table 2 are listed those derivatives of a-sub ethers for whichcomparable vinyl ether derivatives have been prepared. In Table 3 arethose derivatives for which there are no comparable vinyl etherderivatives.

TABLE 2 H3 ROJJ-OOR" and ((4112).. O-Z-OOR" R'=H R=CH3 l/fl l/2 R R"(hrs.) (hrs.)

1 Math 1 t-But l 27.3 25.3 2- 5% dz 3 8(115") 3 fin do 1 mg) o t-Butylperbenzoate Di-t-butyl peroxide TABLE 3 Ether peroxide 1l-methoxy-M-butylperoxy eyclopentaue 2 1-methoxy1-t-butylperoxyeyelohexane l-methoxy-l-t-butylperoxy oycloheptanl-methoxy-l-t-butylperoxy-3,3,5-tr1methylcyeloexane 5a-Methoxy-a-t-butylperoxyethyl benzene life of l-methoxy-l-t-butylperoxycyclohexane would be expected to be close to that of2-methoxy-2-t-butylperoxypropane. Also the cycloheptane derivativeshould be less rather than more stable than the cyclohexane derivative.

Polymerization Studies The ether peroxides were evaluated as initiatorsfor styrene polymerization. Most of the work was bulk polymerization at100 C. and was followed by dilatometry. The remainder of the work was onsuspension polymerization of styrene. In this work t-butyl perbenzoatewas used as a standard and assigned a relative efiiciency of 1.00. Theinitiator concentration used in all this work was 5X10- mole perdeciliter. The polymerization data are summarized in Tables 4 and 5.

TABLE 4.STYRENE POLYMERIZATION AT 100' C.

Peroxide TABLE 5.STYRENE POLYME RIZATION AT 100 C.

It can be seen from Table 2 that the products from or sub vinyl ethersare less thermally stable than from the corresponding unsubstitutedvinyl ether (with the exception of2-methyl-2-t-butylperoxy-tetrahydropyran). This is not unreasonablesince a methyl group (R' in Table 2) has a larger Inductomeric effectthan a hydrogen atom.

It can be seen from Table 3 that the cyclic compounds are far lessstable than the acyclic compounds of Table 2. Ring strain is not theentire explanation since cyclohexane is essentially free of strain andthus the half- Relative efli- Peroxide ciency 1l-methoxy-l-t-butylperoxyeyelopentane 0.73l-methoxy-1-t-buty1peroxycyelohexane. 0.881-methoxy-1-t-butylperoxyeycloheptane 0.65 41-methoxy-1-i-butylperoxy-3,3,5-trimethylcyelw hexane 0.86 5....-a-Methoxy-a-bbutylperoxyethylbenzene 0.97

The ether peroxides of the invention as a class are fairly efficientinitiators and the etficiency does not drop off appreciably at highconversion.

In all cases where comparisons can be made, the ether peroxides of theinvention are more efiicient than the unsubstituted vinyl ether productsand in several examples 7 the difference is quite large, e.g.2-methoxy-2-t-butylperoxy propane and 2-methoxy-2-cumylperoxy propaneare 70% and 55% more efficient than the corresponding products frommethyl vinyl ether. Also 2-methyl-2-tbutylperoxytetrahydropyran is 65%more efiicient than 2-t-butylperoxytetrahydropyran.

The relative efiiciencies for the cyclic ether peroxides in Table areprobably conservative. The temperature R and R are lower alkyl; R, islower alkyl or phenyl; and *R -CR taken together, may form acycloalkylene ring containing 5 to 7 carbon atoms. 2. The ether peroxideof Claim 1 where R and R are methyl.

3. Ether peroxide having the formula R1 at WhlCh they were evaluatedprobably higher than the R O I 00 R optimum for compounds withhalf-lives of 1 to 4 hours. 3 (|J In Table 6, 2-methoxy-2-t-butylperoxypropane is com- 10 4 pared with known peroxides of related structures inorder i hi h R i -b 1; to show its superiority as an initiator. Thetetrahydrofuran R i lower lk d peroxide is also compared with the knownbis-peroxide R C-R taken together, form a cycloalkylene ring of slmrlarstructure. containing 5 to 7 carbon atoms.

TABLE 6 Relative efliciencies Molec- Act. ular tun oxygen Peroxide Wt.(100) basis basis 1 t-Butyl perbenzoate 194 19.3 1.00 1.00 2...2-methoxy-Z-t-butylperoxypropane 162 25.3 1.14 1.33 3.a-Methoxy-a-t-butylperoxyethane. 148 27. 3 0. 68 0. 89 4. 2, 2-bis(t-butylperoxy) propane.. 220 28.4 0. 67 1.18 5. t-Butyl eracetate 13212.5 .85 1.25 6. 2-methy -2-t-butylperoxytetrahydrofuran (a) 174 44. 4:0. 90 1. 01 2, 5-dimethyl-2,5-bis(t-butylperoxy) tetrahydrofuran (b)...276 35. 1 0. 66 0.93

Nora:

CH: HaC /CH: 000(CH1): (01101000 0/ 000(0113).

Since it was thought that our ether peroxides might be susceptible tohydrolysis and therefore useless in suspension or emulsionpolymerization, a series of suspension polymerizations of styrene at 115with three ether peroxides of t-butyl perbenzoate as a control, werecarried out.

The following conclusions are drawn: The relative efficiencies of ourether peroxides drop somewhat it the pH of the suspension drops below 7.However above pH 7 the eificiency correlates exceptionally well withthat obtained in high conversion bulk polymerization. The relativeefiiciency of Z-methoxy-t-butylperoxy propane at pH 7.2 was 1.19compared to 1.18 as observed in high conversion bulk polymerization.

Thus our ether peroxides will complement rather than replace theperoxyesters in suspension polymerization; the peroxyesters being betteron the acid side and our ether peroxides better on the alkaline side,where peroxyesters would suffer saponification.

Thus having described the invention, what is claimed is:

1. Ether peroxide having the formula R: mo-JJ-oom it. in which R, is

4. 2-methoxy-2-cumylperoxy propane. 5. l-methoxy-l-t-butylperoxy 3,3,5trimethylcyclohexane.

References Cited UNITED STATES PATENTS 3,555,099 1/1971 Ballini et al.260-610 2,776,319 1/1957 Ropp 260-610 3,030,386 4/1962 Weissermel et a1.260-3459 FOREIGN PATENTS 1,458,776 10/1966 France 260-610 1,078,1273/1960 Germany 260-610 OTHER REFERENCES W. B. LOVE, Assistant ExaminerUS. Cl. X.R.

- d 7 UNITED STATES PA'IENT OFFICE CERTIFICATE OF CO EQTIUN Patent No. q7 3 Dated .Tn'ly 7 mm qfl Antonio Joseph D'Anqelo, et al It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown 'below:

Column 2, Line 1 25, Insert after the word "isopropylfl' It' ispreferred that R be lower al-kyl, cyclohexyl,

or phenylh.-'-,-

column 5, Table 1, No. 16, "1.4821" should read Column 5, Table 1, No.17, "102" should read --l20f Column 6, Line 47, in the formula, "cc-ooR" COR" should read -C Column 8, line 12 "R should read -R 3 1Column 8, line 13, "R should read --R I Signed and sealed this 11th dayof March 1975.

(SEAL) Attest:

l C. MARSHALL DANN RUTH C. MASON t Commissioner of Patents AttestingOfficer and Trademarks

